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United States Department of Agriculture

Agricultural Research Service

Title: Assessment of Developmental Changes in Chicken and Turkey Insulin-Like Growth Factor-Ii (Cigf-Ii) by Homologous Radioimmunoassay.

Authors
item McMurtry, John
item Rosebrough, Robert
item Brocht, Donna
item Francis, G. - SOUTH AUSTRALIA
item Upton, Z - SOUTH AUSTRALIA
item Phelps, P - EMBREX INC., NC

Submitted to: Journal of Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 30, 1998
Publication Date: N/A

Interpretive Summary: An understanding of the endocrine factors regulating differentiation, growth, and metabolism in avian species are needed so that the potential for maximizing hatchability and genetic potential can be realized. Innovative methods are needed to monitor these growth factors in the circulation and tissues. Previous methods for quantifying avian insulin-like growth factor II (IGF-II) have relied on mammalian radioimmunoassay reagents. There is enough basic structure difference between mammalian and avian IGF-II that utilizing mammalian reagents may not accurately reflect true IGF-II concentrations in various tissues. In that vain a radioimmunoassay was developed for chicken IGF-II. The antibody was characterized and found to be highly specific for IGF-II. Samples were collected from growing chickens and turkeys and analyzed for IGF-II content and the results demonstrated that the concentration of these peptide hormones in the general circulation are much greater than previously reported. The application of the homologous RIA to monitor blood and tissue IGF-II levels during embryonic development and post-hatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-II in growth and metabolism of domestic birds. The results of this study will be of interest to other scientists.

Technical Abstract: The development of a homologous radioimmunoassay (RIA) for chicken insulin-like growth factor-II (cIGF-II) and its application to investigate the developmental changes in IGF-II in the chicken and turkey is described. A double antibody RIA has been developed using recombinantly-derived cIGF-II as antigen, radiolabelled tracer and standard. The resulting immunoassay has a minimum detection limit of 78 pg and effective dose (ED50) of 990 pg. Serial dilutions of chicken and turkey plasma were parallel to serial dilutions of cIGF-II standard. The antiserum is specific for IGF-II as no cross-reactivity with chicken IGF-I, insulin, or glucagon was observed. We have also established that acid-ethanol extraction of chicken and turkey plasma reduced possible interference of insulin-like growth factor binding proteins (IGFBP) in the RIA. Comparison of IGF-II immunoactivity in unextracted and acid/ethanol extracted samples following gel filtration under acidic and neutral conditions indicates that the cIGFBPs may be acid labile. The application of the homologous RIA to monitor plasma levels during embryonic development and post-hatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-II in growth and metabolism of domestic birds.

Last Modified: 4/16/2014
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